The overall objective and long term goal of the proposed research is 1) to understand the optical and physiological function of structures in the optical train with dimensions near the wavelengths of light. Examples of such structures are the photoreceptor organelles, photoreceptor cell inner segments and shielding pigment; and 2) to understand the relation between the photoreceptor cell ionic environment, photoreceptor cell physiological activity, excitation, and adaptation and extracellularly recorded field potentials.